1. Field of the Invention
The subject invention relates to a method of using a syringe to draw a sample of fluid and to deliver the fluid to a point-of-care testing cartridge. The subject invention also relates to a kit of parts that can be used with a portable clinical analyzer for point-of-care clinical analysis of a sample of fluid drawn from a patient.
2. Description of the Related Art
Many medical procedures require diagnostic tests to be performed on a sample of a patient's fluid. Fluid often is collected from a patient by employing a needle holder assembly and one or more evacuated tubes. The tubes are labeled carefully and shipped to a laboratory for analysis. The results of the laboratory analysis then are reported back to the health care provider. The results, of course, could be rushed in emergency situations, but absent an emergency would require more then one day between the time the sample is drawn from the patient to the time that the laboratory analysis is reported to the health care provider.
Devices have been developed for performing at least certain diagnostic tests on a sample of fluid at the point-of-care. The point-of-care diagnostic equipment includes a syringe for receiving a sample of fluid from a patient, a small disposable testing cartridge for receiving a portion of the fluid from the syringe and a portable clinical analyzer for analyzing the fluid and outputting the results. Combinations of testing cartridges and portable clinical analyzers are marketed in the United States by i-STAT Corporation, AVL Scientific Corporation and Diametrics Medical, Inc. The systems produced by these and other companies share certain common features. In particular, the testing cartridge of each system typically has a small rectangular housing about 1″×2″ and about 0.25″ thick. The housing includes an internal reservoir with a volume of between about 65 μl and 110 μl. An inlet port extends through an external wall of the testing cartridge and communicates with the internal reservoir. The cartridge further includes contact pads and sensors that can be placed in communication with the portable clinical analyzer. An example of an i-STAT point-of-care testing cartridge is shown in U.S. Pat. No. 5,638,828.
The prior art point-of-care testing systems are employed with a syringe to draw a sample of fluid from a patient. The syringe then is used to eject a portion of the fluid sample into the inlet port of the point-of-care testing cartridge. The inlet port of the cartridge then is closed and the cartridge is placed in communication with the portable clinical analyzer for performing certain specified diagnostic tests on the sample of fluid in the cartridge. The analyzer then provides a very quick output of the test results without the need for sending the fluid sample to the laboratory.
Point-of-care testing systems provide several efficiencies over systems that require virtually all diagnostic tests to be performed at a location remote from the point-of-care. The small size of the testing cartridge facilitates storage and shipment of the cartridges while also contributing to the portability of the system. However, with regards to transferring a collected sample to the cartridge, the small cartridges can be very difficult to use. For example, alignment of the distal end of the syringe with the inlet port of the testing cartridge can be complicated and difficult. A misalignment or imprecise mating of the syringe with the inlet port of the testing cartridge can lead to a loss of a portion of the collected fluid sample. Fluid that is not delivered efficiently from the syringe into the inlet port of the testing cartridge create the potential for disease transmission. Similarly, a loss of fluid during the transfer from the syringe to the testing cartridge can leave an insufficient volume of fluid for performing the required diagnostic tests. An insufficient volume of fluid to perform the required tests can require the health care worker to return to the patient for a second sample of fluid. This is time consuming for the health care worker and traumatic for the patient. Additionally, some testing cartridges may require an insufficiently filled cartridge to be discarded and a new cartridge to be employed with the new sample of fluid. Thus, inefficiencies in the transfer of fluid from the syringe to the testing cartridge can generate excess costs for additional testing cartridges.
IV access systems of tubes and fittings often are used for delivering liquid solutions to a patient. One such fitting is a blunt plastic tube with opposed proximal and distal ends and a lumen extending therebetween. Portions of the lumen adjacent the proximal end of the plastic fitting define a large tapered opening dimensioned to achieve a fluid-tight engagement with the tapered tip of a fitting, such as the tip at the distal end of a syringe. The proximal end of the plastic fitting includes a pair of diametrically opposite lugs that are configured for engagement with the internal threads on a collar. Threaded engagement of the lugs on the plastic fitting with the internal threads of the collar cause the tip of the fitting to telescope tightly into the tapered entry to the lumen of the plastic fitting. Thus, the prior art plastic fitting can achieve a secure mechanical connection with a collar and a fluid-tight connection with the distal tip of the fitting. The extreme distal tip of the plastic fitting terminates in a single axially aligned egress port with a diameter similar to the diameter of the lumen. Thus, the distal end of the plastic fitting is not beveled to a sharp point. Plastic fittings of this type are sold by Baxter and Becton Dickinson under the trademark INTERLINK®.
Plastic fittings have been used for a variety of medical purposes, including the injection of drugs into the fitting of an IV line. The plastic fittings, however, typically have not been used for phlebotomy or during any diagnostic procedures conducted after a sample of fluid has been collected.
Sharply pointed metallic needle cannulas have many essential uses in medical practice. However, a sharply pointed metallic needle cannula creates the potential for accidental sticks. Thus, sharply pointed metallic needle cannulas are avoided whenever practical. Plastic cannulas are a suitable substitute for sharply pointed metallic cannulas in many situations, including those situations where a cannula must pierce a septum. The prior art plastic cannula is unitarily molded from plastic and includes a proximal end, a distal end and a lumen extending between the ends. The lumen is widely open and tapered at the proximal end of the plastic cannula and is configured for fluid-tight frictional engagement over the tapered tip of a typical fitting. The proximal end of a plastic cannula may further include a pair of diametrically opposite lugs that are dimensioned and configured for engagement with the threads of a collar.
The distal end of the prior art plastic cannula includes a narrow cylindrical wall that surrounds the lumen through the cannula. The narrow cylindrical wall is conically tapered to a point that is sufficiently sharp to pierce a rubber septum. In this regard, the sharpness of the distal tip normally would be limited by the diameter of the lumen through the cannula. This would result in a fairly blunt tip that might not be able to pierce through many septums. However, plastic cannulas have been developed with diametrically opposite triangular extension of the tubular sidewall that converge at the extreme distal end of the plastic cannula. These converging triangular extensions meet at a well defined point at the extreme distal end of the plastic cannula. A pair of identical side ports open transversely at the distal end and at locations between these triangular extensions. A plastic cannula of this type often is used to deliver a drug intravenously through the septum on the above-described fitting. Although the plastic cannula is sufficiently sharp to pierce a septum, it will not accidentally stick a patient.